This study is a multicentre, cross-sectional observational pilot study. The presence of NP was determined based on use of the PainDETECT questionnaire (score 1 to 38), the score of which was defined for the purpose of the study as ≥ 13. A total of 50 OA patients with moderate to severe pain (VAS ≥ 40), 25 without the presence of NP (OA/NP-) (PainDETECT score < 13), and 25 with the presence of NP (OA/NP+) (PainDETECT score ≥ 13) were enrolled. Since this is a pilot study, we arbitrarily determined the number of patients at 50, which represents 25 patients per arm, a number deemed sufficient to identify the knee OA structural changes that could be preferentially associated with NP.